Occupational radiation exposure of medical staff performing ⁹⁰Y-loaded microsphere radioembolization

Feasibility of Liver Transplantation after 90 Y Radioembolization: Lessons from a Radiation Protection Incident

ABSTRACT

Radioembolization using 90 Y is a growing procedure in nuclear medicine for treating hepatocellular carcinoma. Current guidelines suggest postponing liver transplantation or surgical resection for a period of 14 to 30 d after radioembolization to minimize surgeons' exposure to ionizing radiation. In light of a radiation protection incident, we reevaluated the minimum delay required between radioembolization and subsequent liver transplantation. A patient with a hepatocellular carcinoma underwent a liver transplantation 44 h after undergoing radioembolization using 90 Y (860 MBq SIR-Spheres). No specific radioprotection measures were followed during surgery and pathological analysis. We subsequently (1) evaluated the healthcare professionals' exposure to ionizing radiation by conducting dose rate measurements from removed liver tissue and (2) extrapolated the recommended interval to be observed between radioembolization and surgery/transplantation to ensure compliance with the radiation dose limits for worker safety. The surgeons involved in the transplantation procedure experienced the highest radiation exposure, with whole-body doses of 2.4 mSv and extremity doses of 24 mSv. The recommended delay between radioembolization and liver transplantation was 8 d when using SIR-Spheres and 15 d when injecting TheraSphere. This delay can be reduced further when considering the specific 90 Y activity administered during radioembolization. This dosimetric study suggests the feasibility of shortening the delay for liver transplantation/surgery after radioembolization from the 8th or 15th day after using SIR-Spheres or TheraSphere, respectively. This delay can be decreased further when adjusted to the administrated activity while upholding radiation protection standards for healthcare professionals.

Main challenges in radiation protection with emerging radionuclide therapies

The recent development of radionuclide therapy and radioligand therapy has raised a call for achieving the highest quality standards, for either radiopharmacy or radiation protection. Novel radionuclides are now being used, either under the form of in-house production radiopharmaceuticals or available from companies. Over the last 20 years, they include radiolabeled microspheres for selective internal radiotherapy (SIRT), the introduction of the first commercially available alpha emitter radiopharmaceutical, ²²³Ra, and the radiosynoviorthesis which is highly variable across Europe. More important is the development of radioligand therapy, often called theranostics. In this concept, a diagnostic radiopharmaceutical can determine the chance of success of a therapeutic one. Typically, diagnostic radiopharmaceuticals for positron emission tomography, are labeled with ¹⁸F or ⁶⁸Ga, such as the PSMA ligands or somatostatin analogs, and the therapeutic radiopharmaceutical is labeled with ¹⁷⁷Lu. This has revolutionized the world of Nuclear Medicine, but also all concepts that shall be applied to properly apply quality assurance and radiation protection in the field. This article will follow the example of ¹³¹I as the main used radionuclide for therapy during the last 80 years. Proposals can be general, and in parallel expert's articles will give specific guidance on issues with particular radionuclides, i.e., alpha emitters and ¹⁷⁷Lu. This article will also give insight in the radiation protection issues related to the use of microspheres radiolabeled with either ⁹⁰Y or ¹⁶⁶Ho.

Radiation dose aspects and establishment of diagnostic reference levels for90Y radioembolisation during angiographic procedure

⁹⁰Y radioembolisation (RE) is an angiographic procedure used in patients with both primary and secondary hepatic malignancies. Local tumour control can be achieved by short range tumour irradiation by the regional intra-arterial administration of glass or resin microspheres loaded with 90yttrium that accumulate in the tumorous tissue. The aim of this study was to investigate the radiation exposure of RE and to establish a local diagnostic reference level (DRL). In this retrospective study, dose data from 397 procedures in 306 patients (mean age 67.4 ± 10.6 years, 82 female) who underwent RE between 06/2017 and 01/2022 using one of two different angiography systems were analysed. DRL was set as the 75th percentile of the dose distribution. In the overall population, dose area product (DAP) (median (interquartile range, IQR)) was 26 Gy cm²(IQR 12-50) with a median fluoroscopy time (FT) of 4.5 min (IQR 2.9-8.0). FT and DAP increased significantly with the number of infusion positions (median, IQR): one position 23 Gy cm²(12-46), two positions 33 Gy cm²(14-60), three positions 50 Gy cm²(24-82) (p< 0.0001). Local DRL is 47 Gy cm²for RE and 111 Gy cm²for RE with additional embolisation. Radiation exposure and FT are significantly higher with increasing number of infusion positions as well as additional embolisation. Our established DRLs for RE may serve as a benchmark for dose optimisation.

Embolization therapy with microspheres for the treatment of liver cancer: State-of-the-art of clinical translation

Embolization with microspheres is a therapeutic strategy based on the selective occlusion of the blood vessels feeding a tumor. This procedure is intraarterially performed in the clinical setting for the treatment of liver cancer. The practice has evolved over the last decade through the incorporation of drug loading ability, biodegradability and imageability with the subsequent added functionality for the physicians and improved clinical outcomes for the patients. This review highlights the evolution of the embolization systems developed through the analysis of the marketed embolic microspheres for the treatment of malignant hepatocellular carcinoma, namely the most predominant form of liver cancer. Embolic microspheres for the distinct modalities of embolization (i.e., bland embolization, chemoembolization and radioembolization) are here comprehensively compiled with emphasis on material characteristics and their impact on microsphere performance. Moreover, the future application of the embolics under clinical investigation is discussed along with the scientific and regulatory challenges ahead in the field. STATEMENT OF SIGNIFICANCE: Embolization therapy with microspheres is currently used in the clinical setting for the treatment of most liver cancer conditions. The progressive development of added functionalities on embolic microspheres (such as biodegradability, imageability or drug and radiopharmaceutical loading capability) provides further benefit to patients and widens the therapeutic armamentarium for physicians towards truly personalized therapies. Therefore, it is important to analyze the possibilities that advanced biomaterials offer in the field from a clinical translational perspective to outline the future trends in therapeutic embolization.

EANM procedure guideline for the treatment of liver cancer and liver metastases with intra-arterial radioactive compounds

Primary liver tumours (i.e. hepatocellular carcinoma (HCC) or intrahepatic cholangiocarcinoma (ICC)) are among the most frequent cancers worldwide. However, only 10-20% of patients are amenable to curative treatment, such as resection or transplant. Liver metastases are most frequently caused by colorectal cancer, which accounts for the second most cancer-related deaths in Europe. In both primary and secondary tumours, radioembolization has been shown to be a safe and effective treatment option. The vast potential of personalized dosimetry has also been shown, resulting in markedly increased response rates and overall survival. In a rapidly evolving therapeutic landscape, the role of radioembolization will be subject to changes. Therefore, the decision for radioembolization should be taken by a multidisciplinary tumour board in accordance with the current clinical guidelines. The purpose of this procedure guideline is to assist the nuclear medicine physician in treating and managing patients undergoing radioembolization treatment. PREAMBLE: The European Association of Nuclear Medicine (EANM) is a professional non-profit medical association that facilitates communication worldwide among individuals pursuing clinical and research excellence in nuclear medicine. The EANM was founded in 1985. These guidelines are intended to assist practitioners in providing appropriate nuclear medicine care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by medical professionals taking into account the unique circumstances of each case. Thus, there is no implication that an approach differing from the guidelines, standing alone, is below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set out in the guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources or advances in knowledge or technology subsequent to publication of the guidelines. The practice of medicine involves not only the science but also the art of dealing with the prevention, diagnosis, alleviation and treatment of disease. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be recognised that adherence to these guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources and the needs of the patient to deliver effective and safe medical care. The sole purpose of these guidelines is to assist practitioners in achieving this objective.

Review of extremity dosimetry in nuclear medicine

The exposure of the fingers is one of the major radiation protection concerns in nuclear medicine (NM). The purpose of this paper is to provide an overview of the exposure, dosimetry and protection of the extremities in NM. A wide range of reported finger doses were found in the literature. Historically, the highest finger doses are found at the fingertip in the preparation and dispensing of¹⁸F for diagnostic procedures and⁹⁰Y for therapeutic procedures. Doses can be significantly reduced by following recommendations on source shielding, increasing distance and training. Additionally, important trends contributing to a lower dose to the fingers are the use of automated procedures (especially for positron emission tomography (PET)) and the use of prefilled syringes. On the other hand, the workload of PET procedures has substantially increased during the last ten years. In many cases, the accuracy of dose assessment is limited by the location of the dosimeter at the base of the finger and the maximum dose at the fingertip is underestimated (typical dose ratios between 1.4 and 7). It should also be noted that not all dosimeters are sensitive to low-energy beta particles and there is a risk for underestimation of the finger dose when the detector or its filter is too thick. While substantial information has been published on the most common procedures (using^99mTc,¹⁸F and⁹⁰Y), less information is available for more recent applications, such as the use of⁶⁸Ga for PET imaging. Also, there is a need for continuous awareness with respect to contamination of the fingers, as this factor can contribute substantially to the finger dose.

Yttrium-90 Radioembolization in the VX2 Rabbit Model: Radiation Safety and Factors Influencing Delivery Efficiency

The purpose of this study was to define the optimal infusion parameters and operator radiation exposure for yttrium-90 (⁹⁰Y) radioembolization in the VX2 rabbit model of liver cancer. Forty-one rabbits with VX2 were treated with glass microspheres with vial sizes of 1, 3, and 5 GBq. The mean administered activity was 51.5 MBq (95% CI, 39.1-63.9). Delivery efficiency improved with 1 GBq versus with 3 GBq (residual 11.0% vs 46.4%, respectively; P = .0013) and improved with 1 GBq versus with 5 GBq (residual 11.0% vs 33.8%, respectively; P = .0060). The mean operator extremity exposure was 41.7 μSv/infusion. The optimal minimum infusion volume and rate was 49 mL and 21 mL/min, respectively. Fecal elimination occurred with microsphere uptake in the gallbladder at 1 and 2 weeks. ⁹⁰Y radioembolization can be safely and efficiently performed in the VX2 rabbit model. Methodological considerations as a "how-to" for the setup of a preclinical ⁹⁰Y laboratory are included to support future translational research.

Radiation exposure of the operators in the preparation and administration of yttrium-90 microspheres in the treatment of malignant hepatic lesions: What is the risk?

Liver radioembolization is an emerging treatment against liver primary and secondary tumours. The whole procedure of radioembolization involves different health care specialists with different expertise. During the fractionation and infusion phases, the personnel manipulates high activities of ⁹⁰Y. In our centre, the number of radioembolization treatments per year is increasing; the aim of this study is to monitor the dose to the operators and to estimate the radiological risk for the operators involved in the RE. At present, two medical devices are approved: Sir-Sphere® and Therasphere™, both loaded with ⁹⁰Y. The dosimeters used were TLDs placed over the fingertips, for a total of 4 dosimeters for each phase; the selected dose descriptor was Hp_0.07. The study concerned 17 patients affected by malignant hepatic lesions, treated from September 2017 to March 2018. We performed 27 procedures: 10 fractionations (with Sir-Sphere®) and 17 infusions to the patients (10 with Sir-Spheres®, 7 with Theraspheres™). For fractionation phase, the average activity of each preparation was 3.34 GBq, the average value of Hp_0.07 was 0.50mSv. For infusion phase, the average activity was 1.51 GBq for Sir-Sphere® and 2.10 GBq for Theraspheres™, the average value of Hp_0.07 was 0.10mSv. No significant differences were found between senior (Hp_0.07 = 0.08mSv) and young operators (Hp_0.07 = 0.09mSv), respectively. Similarly, no significant differences were found between the right and left hand, with the same average value of Hp_0.07 (0.01mSv). In conclusion, the results are encouraging, since fingertips reported doses very low. The handling of ⁹⁰Y microspheres and the radioembolization procedure can be carried out under safe conditions.

Labeling of Hinokitiol with 90Y for Potential Radionuclide Therapy of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC), the most common form of primary liver tumors, is the fifth cancer in the world in terms of incidence, and third in terms of mortality. Despite significant advances in the treatment of HCC, its prognosis remains bleak. Transarterial radioembolization with radiolabeled microspheres and Lipiodol has demonstrated significant effectiveness. Here we present a new, simple radiolabeling of Lipiodol with Yttrium-90, for the potential treatment of HCC.

Radiation exposure of the operators in the preparation and administration of yttrium-90 microspheres in the treatment of malignant hepatic lesions: what is the risk?

Liver radioembolization (RE) is an emerging treatment against liver primary and secondary tumours. The whole procedure of RE involves different health care specialists with different expertise. During the fractionation and infusion phases, the personnel manipulates high activities of ⁹⁰Y. In our centre, the number of RE treatments per year is increasing; the aim of this study is to monitor the dose to the operators and to estimate the radiological risk for the operators involved in the RE. At present, two medical devices are approved: Sir-Sphere® and Therasphere™, both loaded with ⁹⁰Y. The dosimeters used were TLD placed over the fingertips, for a total of four dosimeters for each phase; the selected dose descriptor was Hp_0.07. The study concerned 17 patients affected by malignant hepatic lesions, treated from September 2017 to March 2018. We performed 27 procedures: 10 fractionations (with Sir-Sphere®) and 17 infusions to the patients (10 with Sir-Spheres®, seven with Theraspheres™). For fractionation phase, the average activity of each preparation was 3.34 GBq, the average value of Hp_0.07 was 0.50 mSv. For infusion phase, the average activity was 1.51 GBq for Sir-Sphere® and 2.10 GBq for Theraspheres™, the average value of Hp_0.07 was 0.10 mSv. No significant differences were found between senior (Hp_0.07 = 0.08 mSv) and young operators (Hp_0.07 = 0.09 mSv), respectively. Similarly, no significant differences were found between the right and left hand, with the same average value of Hp_0.07 (0.01 mSv). In conclusion, the results are encouraging, since fingertips reported doses very low. The handling of ⁹⁰Y microspheres and the RE procedure can be carried out under safe conditions.

Epidemic characteristics and related risk factors of occupational exposure for pediatric health care workers in Chinese public hospitals: a cross-sectional study

Background

Health care workers have a high risk of occupational exposure. However, the risk of occupational exposure for pediatric health care workers has not been acknowledged in previous studies. The purpose of this study was to investigate the occupational exposure rate of pediatric health care workers in Chinese public hospitals, to explore risk factors for occupational exposure, and to put forward corresponding countermeasures to reduce occupational exposure of pediatric health care workers and protect their physical and mental health.

Methods

A cross-sectional study was conducted with pediatric health care workers in 43 hospitals in 15 provinces in eastern, central, and western China between July and October 2018. With this sample, we computed the descriptive statistics of the demographic characteristics, calculated the frequency of various types of occupational exposure, and tested risk factors for occupational exposure using a chi-squared test and binary logistic regression analysis.

Results

Most respondents were nursing staff (61.1%) and workers with a low-ranking professional title (50.5%). The most common style of occupational exposure in our sample was a hazard in the work environment (62.6%). Notably, physicians were less likely to experience occupational exposure than nurses (OR = 0.320, 95% CI = 0.241, 0.426). Meanwhile, pediatric health care workers who interpreted the doctor-patient relationship as harmonious (OR = 0.304, 95% CI = 0.152, 0.607) were less likely to suffer occupational exposure.

Conclusion

Pediatric health care workers in Chinese public hospitals have a high occupational exposure risk and the risk factors are complex and diverse. The state, society, hospitals should acknowledge this issue and develop strategies to protect the physical and mental health of pediatric health care workers.

RADIATION EXPOSURE TO OPERATORS PERFORMING PHARMACOLOGIC STRESS TESTING IN 99mTc MYOCARDIAL PERFUSION IMAGING: A PROSPECTIVE STUDY

This prospective study investigated radiation exposure dose (RED) to main operator (MO) and supervisory operator (SO) performing dypiridamole stress testing in a 1-d rest/stress 99mTc tetrofosmin single-photon emission computed tomography (SPECT) of consecutive 42 patients. MO was instructed to be close to the patients during the entire procedures including the vasodilator and radiotracer injection. SO mainly recorded the data on the procedures apart from the patients. RED, procedure time (PT) and internal radioactivity (IR) of patients were measured before and after a secondary tracer injection for stress SPECT, respectively. RED was significantly greater to MO than to SO (6.2 ± 2.7 vs 2.5 ± 2.1 μSV per stress procedure, p < 0.0001). Multivariate analyses revealed that IR and PT were significantly independent factors to predict RED to both operators. Operators performing pharmacologic stress procedure should be aware that IR and PT are independent factors for RED in 99mTc myocardial perfusion imaging.

Targeted Radionuclide Therapy: An Evolution Toward Precision Cancer Treatment

OBJECTIVE

This article reviews recent developments in targeted radionuclide therapy (TRT) approaches directed to malignant liver lesions, bone metastases, neuroendocrine tumors, and castrate-resistant metastatic prostate cancer and discusses challenges and opportunities in this field.

CONCLUSION

TRT has been employed since the first radioiodine thyroid treatment almost 75 years ago. Progress in the understanding of the complex underlying biology of cancer and advances in radiochemistry science, multimodal imaging techniques including the concept of "see and treat" within the framework of theranostics, and universal traction with the notion of precision medicine have all contributed to a resurgence of TRT.